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arXiv:2606.03884

20 Second Parity Lifetime in an InAs--Pb Tetron Device

Morteza Aghaee, Zulfi Alam, Mariusz Andrzejczuk, Andrey Antipov, Theodora Asimakidis, Mikhail Astafev, Lukas Avilovas, Ahmad Azizimanesh, Amin Barzegar, Bela Bauer, Jonathan Becker, Umesh Kumar Bhaskar, Andrea G. Boa, Srini Boddapati, Nichlaus Bohac, Jouri Bommer, Jan Borovsky, Léo Bourdet, Samuel Boutin, Srivatsa Chakravarthi, Benjamin J. Chapman, Nikolaos Chatzaras, Tzu-Chiao Chien, Jason Cho, Patrick T. Codd, William Cole, Paul W. Cooper, Fabiano Corsetti, Ajuan Cui, Tareq El Dandachi, Konstantinos Divanis, Clayton Doyle, Andreas Ekefjard, Javier A. Falcon, Saeed Fallahi, Luca Galletti, Geoffrey C. Gardner, Haris Gavranovic, João Pedro Morais Gomes, Deshan Govender, Flavio Griggio, Ruben Grigoryan, Sebastian Grijalva, Sergei Gronin, Jan Gukelberger, Marzie Hamdast, Esben Bork Hansen, Sebastian Heedt, Samantha Ho, Laurens Holgaard, Kevin van Hoogdalem, Jinnapat Indrapiromkul, Henrik Ingerslev, Lovro Ivancevic, Max Jantos, Thomas Jensen, Jaspreet Singh Jhoja, Vidul R. Joshi, Konstantin V. Kalashnikov, Ray Kallaher, Rachpon Kalra, Farhad Karimi, Torsten Karzig, Maren Elisabeth Kloster, Christina Knapp, Jonathan Knoblauch, Jonne Koski, Anders Kringhøj, Tom Laeven, Jeffrey Lai, Gijs de Lange, Thorvald W. Larsen, Kyunghoon Lee, Kongyi Li, Shuang Liang, Tyler Lindemann, Luna Lochmatter, Marijn Lucas, Roman Lutchyn, Morten Hannibal Madsen, Nasiari Madulid, Ivan Maliyov, Yanick Mampaey, Michael Manfra, Signe Brynold Markussen, Esteban A. Martinez, J. R. Mattinson, Mónica Meira, Camille A. Mikolas, Sarang Mittal, Gopakumar Mohandas, Christian Mollgaard, Michiel W. A. de Moor, Chris Moore, George Moussa, Bhargav Nabar, Anirudh Narla, Ahmad Naseri, Chetan Nayak, Bjørn Funch Schrøder Nielsen, Jens Hedegaard Nielsen, Michael J. Nystrom, Eoin O'Farrell, Keita Ohtani, Theodore Rex Orth, Sara Di Paolo, Camille Papon, Luca Petit, Dima Pikulin, Mohana Rajpalke, Alejandro Alcaraz Ramirez, Katrine Rasmussen, David Razmadze, Yuan Ren, Mariya Romanova, Loïc Roure, Ivan Sadovskyy, Lauri Sainiemi, Juan Carlos Estrada Saldaña, Irene Sanlorenzo, Tatiane Pereira dos Santos, Carl Vincent C. Saruda, Simon Schaal, John Schack, Emma R. Schmidgall, Christina Sfetsou, Cristina Sfiligoj, Zahra Shekason, Sarat Shankar Sinha, Patrick Sohr, Maria João Lourenço de Sousa, Kasper Roed Spiegelhauer, Tomas Stankevic, Henri J. Suominen, Judith Suter, Attila Szénási, Samuel M. L. Teicher, Naganivetha Thiyagarajah, Raj Tholapi, Mason Thomas, Dennis Tom, Emily Toomey, Joshua Tracy, Michelle Turley, Matthew D. Turner, Ivan Urban, Aakash Valliappan, Dmitrii V. Viazmitinov, Anna Wulff Viazmitinova, Dominik Johannes Vogel, Wenbo Wang, Christopher A. Watson, John Watson, Alex Webster, Joseph Weston, Timothy Williamson, Georg W. Winkler, David J. van Woerkom, Brian Paquelet Wuetz, Cécile X. Yu, Emrah Yucelen, Jesús Herranz Zamorano, Roland Zeisel, Guoji Zheng, A. M. Zimmerman

cond-mat.mes-hallquant-phSubmitted Jun 2, 2026• Announced Jun 3, 2026• Revised Jun 3, 2026 (v2)
v1 · Jun 2, 2026v2 · Jun 3, 2026
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Abstract

A central promise of topological quantum computing is that increasing the excitation gap improves device performance significantly. Here, we experimentally validate this principle in an InAs--Pb tetron device via interferometric single-shot parity measurements. By replacing aluminum with the higher-gap superconductor lead in our superconductor-semiconductor hybrid devices, we have improved the robustness of our topological phase. In addition, to enable fast and precise bring-up at scale, we have developed an rf measurement technique that resolves low-energy wire-end states and directly measures their energy splitting with $μ\text{eV}$ precision. We employ this technique to bring up a device in a multi-tetron array and perform parity measurements of one of the tetron's hybrid nanowires (NWs). By controllably switching the wire parity, we observe $h/2e$-periodic bimodal shifts in the quantum capacitance of a quantum dot coupled to the hybrid nanowire in an interference loop. Further time-resolved measurements reveal a characteristic parity switching time of $\sim 20$ s with some instances reaching minute-scale. Such extremely long parity lifetimes are orders of magnitude longer than typical qubit operation times, which are on the order of $μ\text{s}$. Finally, we discuss potential implications for the fidelity of Pauli measurements.

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The fusion of non-Abelian anyons is a fundamental operation in measurement-only topological quantum computation1. In one-dimensional topological superconductors (1DTSs)2–4, fusion amounts to a determination of the shared fermion parity of Majorana zero modes (MZMs). Here we introduce a device architecture5 that is compatible with future tests of fusion rules. We implement a single-shot interferometric measurement of fermion parity6–11 in indium arsenide–aluminium heterostructures with a gate-defined superconducting nanowire12–14. The interferometer is formed by tunnel-coupling the proximitized nanowire to quantum dots. The nanowire causes a state-dependent shift of the quantum capacitance of these quantum dots of up to 1 fF. Our quantum-capacitance measurements show flux h/2e-periodic bimodality with a signal-to-noise ratio (SNR) of 1 in 3.6 μs at optimal flux values. From the time traces of the quantum-capacitance measurements, we extract a dwell time in the two associated states that is longer than 1 ms at in-plane magnetic fields of approximately 2 T. We discuss the interpretation of our measurements in terms of both topologically trivial and non-trivial origins. The large capacitance shift and long poisoning time enable a parity measurement with an assignment error probability of 1%. A device architecture based on indium arsenide–aluminium heterostructures with a gate-defined superconducting nanowire allows single-shot interferometric measurement of fermion parity and demonstrates an assignment error probability of 1%.

Nature•Feb 19, 2025•158 citations

Measurement-induced enhancement of the $X$-parity lifetime in a Majorana tetron

Katharina Laubscher, Jay D. Sau, S. Das Sarma

A recent experiment [arXiv:2507.08795] has reported measurements of the interwire $X$-parity lifetime in a Majorana tetron device via the quantum capacitance of an auxiliary readout dot. Motivated by these measurements, we theoretically study the interwire parity lifetime in a minimal model of the coupled dot-tetron system subject to electrostatic noise. We show that coupling to the measurement dot can itself strongly modify the parity dynamics by generating an energy splitting that shifts noise-induced transitions to finite frequency and thereby stabilizes the measured states against low-frequency fluctuations. For representative noise strengths motivated by disordered nanowire devices, we find $X$-parity switching lifetimes of order microseconds in the measurement configuration even when the corresponding bare-tetron coherence time is only tens of nanoseconds long. We analyze both the dispersive regime, where the dot can be integrated out and the dynamics reduces to an effective two-level system, and the near-resonant regime, where all four low-energy states participate. In the latter case, rapid transitions organize the spectrum into two long-lived manifolds that approximately correspond to sectors of the combined dot-tetron $X$-loop parity, yielding effective two-state switching despite the underlying multilevel structure. Our results show that measurement-induced stabilization can substantially enhance the observed $X$-parity switching lifetime, such that the lifetime measured under continuous readout can greatly exceed the intrinsic idle $T_2^*$ coherence time of the isolated Majorana tetron qubit.

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The rate of charge-parity switching in a full-shell superconductor-semiconductor nanowire qubit is measured by directly monitoring the dispersive shift of a readout resonator. At zero magnetic field, the measured switching time scale ${T}_{P}$ is on the order of $100\phantom{\rule{0.16em}{0ex}}\mathrm{m}\mathrm{s}$. Two-tone spectroscopy data post-selected on charge parity is demonstrated. With increasing temperature or magnetic field, ${T}_{P}$ is at first constant, then exponentially suppressed, consistent with a model that includes both nonequilibrium and thermally activated quasiparticles. As ${T}_{P}$ is suppressed, qubit lifetime ${T}_{1}$ also decreases. The long ${T}_{P}\ensuremath{\sim}0.1\phantom{\rule{0.16em}{0ex}}\mathrm{s}$ at zero field is promising for future development of qubits based on hybrid nanowires.

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The properties of superconducting devices depend sensitively on the parity (even or odd) of the quasiparticles that they contain. Encoding quantum information in the parity degree of freedom is central in several emerging solid-state qubit architectures, including in hybrid superconductor-semiconductor devices. In the latter case, accurate, nondestructive, and time-resolved parity measurements are a challenging issue. Here, we report on control and real-time parity measurement in a superconducting island embedded in a superconducting loop and realized in a hybrid two-dimensional heterostructure using a microwave resonator. To avoid microwave losses impeding time-resolved measurements, the device and readout resonator are located on separate chips, connected via flip-chip bonding, and couple inductively through vacuum. The superconducting resonator detects the parity-dependent circuit inductance, allowing for fast parity readout. We have resolved even- and odd-parity states with a signal-to-noise ratio of SNR ≈ 3 for an integration time of 20 μ s and a detection fidelity exceeding 98 % . The real-time parity measurement shows a state lifetime extending into the millisecond range. Our approach will lead to a better understanding of coherence-limiting mechanisms in superconducting quantum hardware and help to advance inductive-readout schemes for hybrid qubits. Published by the American Physical Society 2024

arXiv:2307.06718•PRX Quantum•Aug 20, 2024•7 citations

Proposing one-sided tetrons as topological qubits for Majorana-based quantum computation

Tudor D. Stanescu, Sumanta Tewari

One-dimensional SM-SC hybrid nanowires with Rashba spin-orbit coupling and applied Zeeman field can support Majorana zero modes (MZMs) at the ends of the wire. In finite-length systems, residual wave-function overlap between the end modes produces an energy splitting. In a two-sided tetron qubit, composed of a pair of parallel Majorana wires coupled by a trivial SC backbone in the middle, this splitting limits the parity lifetime associated with Majorana pairs involving both wires and the coherence of the qubit, adversely affecting measurement-based braiding and readout operations. Here, we propose a one-sided tetron made of four parallel Majorana wires connected at a common end by an SC backbone. In the topological phase, the free wire ends host four MZMs that define the topological qubit, while the Majoranas localized near the opposite ends hybridize through the backbone and acquire finite energy. To study the basic hybridization mechanism, we consider a simpler two-wire subsystem, i.e., half of a one-sided tetron, which we call a doublon. In a doublon, the backbone, or bridge, strongly hybridizes the two Majorana modes at the connected end and shifts them away from zero energy, while the modes at the free ends form a near-zero energy fermion. We show that the splitting of the surviving MZM pair can fall by about two orders of magnitude compared to the splitting energies in a two-sided tetron, thereby dramatically increasing the parity lifetimes. Thus, the one-sided tetron ensures a suppression of the Majorana overlap comparable to doubling the length of the corresponding two-sided tetron.

arXiv:2610.07169•Oct 5, 2026•0 citations
A central promise of topological quantum computing is that increasing the excitation gap improves device performance significantly. Here, we experimentally validate this principle in an InAs--Pb tetron device via interferometric single-shot parity measurements. By replacing aluminum with the higher-gap superconductor lead in our superconductor-semiconductor hybrid devices, we have improved the robustness of our topological phase. In addition, to enable fast and precise bring-up at scale, we have developed an rf measurement technique that resolves low-energy wire-end states and directly measures their energy splitting with μeVμ\text{eV}μeV precision. We employ this technique to bring up a device in a multi-tetron array and perform parity measurements of one of the tetron's hybrid nanowires (NWs). By controllably switching the wire parity, we observe h/2eh/2eh/2e-periodic bimodal shifts in the quantum capacitance of a quantum dot coupled to the hybrid nanowire in an interference loop. Further time-resolved measurements reveal a characteristic parity switching time of ∼20\sim 20∼20 s with some instances reaching minute-scale. Such extremely long parity lifetimes are orders of magnitude longer than typical qubit operation times, which are on the order of μsμ\text{s}μs. Finally, we discuss potential implications for the fidelity of Pauli measurements.
The fusion of non-Abelian anyons is a fundamental operation in measurement-only topological quantum computation1. In one-dimensional topological superconductors (1DTSs)2–4, fusion amounts to a determination of the shared fermion parity of Majorana zero modes (MZMs). Here we introduce a device architecture5 that is compatible with future tests of fusion rules. We implement a single-shot interferometric measurement of fermion parity6–11 in indium arsenide–aluminium heterostructures with a gate-defined superconducting nanowire12–14. The interferometer is formed by tunnel-coupling the proximitized nanowire to quantum dots. The nanowire causes a state-dependent shift of the quantum capacitance of these quantum dots of up to 1 fF. Our quantum-capacitance measurements show flux h/2e-periodic bimodality with a signal-to-noise ratio (SNR) of 1 in 3.6 μs at optimal flux values. From the time traces of the quantum-capacitance measurements, we extract a dwell time in the two associated states that is longer than 1 ms at in-plane magnetic fields of approximately 2 T. We discuss the interpretation of our measurements in terms of both topologically trivial and non-trivial origins. The large capacitance shift and long poisoning time enable a parity measurement with an assignment error probability of 1%. A device architecture based on indium arsenide–aluminium heterostructures with a gate-defined superconducting nanowire allows single-shot interferometric measurement of fermion parity and demonstrates an assignment error probability of 1%.
Measurement-induced enhancement of the XXX-parity lifetime in a Majorana tetron
A recent experiment [arXiv:2507.08795] has reported measurements of the interwire XXX-parity lifetime in a Majorana tetron device via the quantum capacitance of an auxiliary readout dot. Motivated by these measurements, we theoretically study the interwire parity lifetime in a minimal model of the coupled dot-tetron system subject to electrostatic noise. We show that coupling to the measurement dot can itself strongly modify the parity dynamics by generating an energy splitting that shifts noise-induced transitions to finite frequency and thereby stabilizes the measured states against low-frequency fluctuations. For representative noise strengths motivated by disordered nanowire devices, we find XXX-parity switching lifetimes of order microseconds in the measurement configuration even when the corresponding bare-tetron coherence time is only tens of nanoseconds long. We analyze both the dispersive regime, where the dot can be integrated out and the dynamics reduces to an effective two-level system, and the near-resonant regime, where all four low-energy states participate. In the latter case, rapid transitions organize the spectrum into two long-lived manifolds that approximately correspond to sectors of the combined dot-tetron XXX-loop parity, yielding effective two-state switching despite the underlying multilevel structure. Our results show that measurement-induced stabilization can substantially enhance the observed XXX-parity switching lifetime, such that the lifetime measured under continuous readout can greatly exceed the intrinsic idle T2∗T_2^*T2∗​ coherence time of the isolated Majorana tetron qubit.
The rate of charge-parity switching in a full-shell superconductor-semiconductor nanowire qubit is measured by directly monitoring the dispersive shift of a readout resonator. At zero magnetic field, the measured switching time scale TP{T}_{P}TP​ is on the order of 100ms100\phantom{\rule{0.16em}{0ex}}\mathrm{m}\mathrm{s}100ms. Two-tone spectroscopy data post-selected on charge parity is demonstrated. With increasing temperature or magnetic field, TP{T}_{P}TP​ is at first constant, then exponentially suppressed, consistent with a model that includes both nonequilibrium and thermally activated quasiparticles. As TP{T}_{P}TP​ is suppressed, qubit lifetime T1{T}_{1}T1​ also decreases. The long ${T}_{P}\ensuremath{\sim}0.1\phantom{\rule{0.16em}{0ex}}\mathrm{s}$ at zero field is promising for future development of qubits based on hybrid nanowires.
We realize a hybrid superconductor-semiconductor transmon device in which the Josephson effect is controlled by a gate-defined quantum dot in an InAs-Al nanowire.Microwave spectroscopy of the transition spectrum of the transmon allows us to probe the ground-state parity of the quantum dot as a function of the gate voltages, the external magnetic flux, and the magnetic field applied parallel to the nanowire.The measured parity phase diagram is in agreement with that predicted by a single-impurity Anderson model with superconducting leads.Through continuous-time monitoring of the circuit, we furthermore resolve the quasiparticle dynamics of the quantum dot Josephson junction across the phase boundaries.Our results can facilitate the realization of semiconductor-based 0-π qubits and Andreev qubits.
The properties of superconducting devices depend sensitively on the parity (even or odd) of the quasiparticles that they contain. Encoding quantum information in the parity degree of freedom is central in several emerging solid-state qubit architectures, including in hybrid superconductor-semiconductor devices. In the latter case, accurate, nondestructive, and time-resolved parity measurements are a challenging issue. Here, we report on control and real-time parity measurement in a superconducting island embedded in a superconducting loop and realized in a hybrid two-dimensional heterostructure using a microwave resonator. To avoid microwave losses impeding time-resolved measurements, the device and readout resonator are located on separate chips, connected via flip-chip bonding, and couple inductively through vacuum. The superconducting resonator detects the parity-dependent circuit inductance, allowing for fast parity readout. We have resolved even- and odd-parity states with a signal-to-noise ratio of SNR ≈ 3 for an integration time of 20 μ s and a detection fidelity exceeding 98 % . The real-time parity measurement shows a state lifetime extending into the millisecond range. Our approach will lead to a better understanding of coherence-limiting mechanisms in superconducting quantum hardware and help to advance inductive-readout schemes for hybrid qubits. Published by the American Physical Society 2024
One-dimensional SM-SC hybrid nanowires with Rashba spin-orbit coupling and applied Zeeman field can support Majorana zero modes (MZMs) at the ends of the wire. In finite-length systems, residual wave-function overlap between the end modes produces an energy splitting. In a two-sided tetron qubit, composed of a pair of parallel Majorana wires coupled by a trivial SC backbone in the middle, this splitting limits the parity lifetime associated with Majorana pairs involving both wires and the coherence of the qubit, adversely affecting measurement-based braiding and readout operations. Here, we propose a one-sided tetron made of four parallel Majorana wires connected at a common end by an SC backbone. In the topological phase, the free wire ends host four MZMs that define the topological qubit, while the Majoranas localized near the opposite ends hybridize through the backbone and acquire finite energy. To study the basic hybridization mechanism, we consider a simpler two-wire subsystem, i.e., half of a one-sided tetron, which we call a doublon. In a doublon, the backbone, or bridge, strongly hybridizes the two Majorana modes at the connected end and shifts them away from zero energy, while the modes at the free ends form a near-zero energy fermion. We show that the splitting of the surviving MZM pair can fall by about two orders of magnitude compared to the splitting energies in a two-sided tetron, thereby dramatically increasing the parity lifetimes. Thus, the one-sided tetron ensures a suppression of the Majorana overlap comparable to doubling the length of the corresponding two-sided tetron.